1. Field of the Invention
The present invention relates to a multichip system in which a plurality of semiconductor chips are synchronously operated based on a clock signal from a clock signal supply unit, and to a method of supplying the clock signal therefor.
2. Description of the Background Art
FIG. 14 is a block diagram of a conventional multichip system. In the conventional multichip system, a plurality of semiconductor chips 1 are provided on a printed circuit board 2. Aluminum wires 3 on the printed circuit board 2 electrically connect the respective semiconductor chips 1 to a clock signal supply unit 4. Thus, all the semiconductor chips 1 are operated in synchronism with each other based on a clock signal S.sub.CL given from the clock signal supply unit 4 through the aluminum wires 3.
In the conventional multichip system, the aluminium wires 3 act as a transmission path for the clock signal S.sub.CL. The lengths of the aluminum wires 3, i.e., transmission distances between the clock signal supply unit 4 and the semiconductor chips 1 are different from each other. Accordingly, periods of time required to transmit the clock signal S.sub.CL from the clock signal supply unit 4 to the respective semiconductor chips 1 (hereinafter referred to as "signal transmission time") are different depending on the transmission distance. In other words, clock skew occurs because of the different lengths of the aluminum wires 3. In particular, the impedance of the aluminum wires 3 increases as the frequency of the clock signal S.sub.CL grows higher. In this case, there has been a practically serious problem that the clock skew is resultingly aggravated as compared with the clock signal S.sub.CL having a low frequency.